correct ISO 9075 strftime formats, missing percent character in hours
removed unused variables in FREEZE/THAW
Changed with_offset
Implemented ->with_offset_same_local and renamed ->with_offset to
->with_offset_same_instant. An alias remain for ->with_offset.
Changed with_offset
Implemented ->with_offset_same_local and renamed ->with_offset to
->with_offset_same_instant. An alias remain for ->with_offset.
Added tests for ->with_offset_same_xxx
use ->with_offset_same_instant